Alterations of the Gut Microbiome and TMAO Levels in Patients with Ulcerative Colitis

<b>Background:</b> Ulcerative colitis (UC) is an idiopathic and heterogeneous large intestine disease, characterized by chronic mucosa and submucosa inflammation. Alteration of the intestinal microbiome in UC may be responsible for modifications in metabolite production. Aim: To investigate the microbiota status and trimethylamine-N-oxide (TMAO) metabolite levels in patients with UC according to clinical and endoscopic activity. <b>Methods:</b> As part of a grant project AP14871959 from September 2022 to October 2023, 31 patients with UC and 15 healthy volunteers over 18 years at the Clinic of NCJSC "KMU" were assessed for blood TMAO level and metagenomic sequencing of fecal microbiome. <b>Results:</b> A significant depletion of the main representatives of Bacteroides, Parabacteroides, Prevotella; and an increase in the relative abundance of the genera Actinomyces, Klebsiella, Limosilactobacillus, Streptococcus, Escherichia-Shigella were detected in patients with UC. The number of p_Actinobacteria (g_Collinsella) and p_Eubacterium (g_Xylanophilum) representatives with genes encoding TMA-trimethylamine conversion is significantly reduced in UC patients. TMAO levels were significantly lower in UC patients than in healthy individuals (0.233 µmol/L, <i>p</i> = 0.004). TMAO decreased with disease severity and significantly differed between patients with different activities (<i>p</i> = 0.034). <b>Conclusions:</b> The composition of the intestinal microbiome changes and the level of TMAO decreases in patients with UC at different activities.